GST spiking boost!! HELP PLEASEE

[willye_br]

HI, i recently sold my 1999 gs spyder and bought a 1996 gst. when i got the car ran beautiful pulled hard. out of nowhere its started acting weird.i have the FORCED PERFORMANCE wastegate actuator with 17lb Spring instead of 11 stock and greddy bov.(circulated). when i take off the boot gauge goes to 15psi-21psi.Anything untill 15 car is goo past 16psi the car shakes maybe fuel cut? i know that the max a t25 can hold is about 16-17 psi. I did put in a walbro 255.

Why is is going past 17psi?

Maybe boost leak?

i want to run 14-15psi max i want to get a hallman boost controller but would that help? thats what im confused about if the spring on the wastegate is 17psi will i be able to decrease boost?

Im new to dsm motors so any help would be appreciated.and i spent all day searching so dont be an a$$ and say use the search button

 

[SD99GST]

HI, i recently sold my 1999 gs spyder and bought a 1996 gst. when i got the car ran beautiful pulled hard. out of nowhere its started acting weird.i have the FORCED PERFORMANCE wastegate actuator with 17lb Spring instead of 11 stock and greddy bov.(circulated). when i take off the boot gauge goes to 15psi-21psi.Anything untill 15 car is goo past 16psi the car shakes maybe fuel cut? i know that the max a t25 can hold is about 16-17 psi. I did put in a walbro 255.

Why is is going past 17psi?

Maybe boost leak?

i want to run 14-15psi max i want to get a hallman boost controller but would that help? thats what im confused about if the spring on the wastegate is 17psi will i be able to decrease boost?

Im new to dsm motors so any help would be appreciated.and i spent all day searching so dont be an a$$ and say use the search button

You sure its a t25? Please fill out your car description or let me know what modifications it has... since it has a upgraded fuel pump I can only assume some other stuff might be modded as well...

 

[willye_br]

well i got the car STOCK and i did the mods.

Injen intake with filter
walbro 255
FP 17lb wastegate actuator
greddy type s
t25 turbo (yes im sure)
stock intercooler
stock 450cc injectors
stock everything else pretty much
i have a cheap ebay MBC hooked up but idk if it works or not

btw WHEN I HAD IT HOOKED UP BEFORE TO STOCK BOOST CONTROLLER it still spiked!!!
any ideas?

 

[SD99GST]

Are you running a AFPR along with that 255? did this problem happen after you upgraded fuel pump?

 

[willye_br]

No i am not familiar with those. should i be running one? and NO i replaced the fuel pump thinking it would fix it maybe the engine was starving for gas.

 

[SD99GST]

Yes you should run a afpr when upgrading fuel pumps... And also I dont recommend you do any fuel system changes until you have something to accommodate them like a safc or link.

So completly stock the car of course ran fine, then without doing any upgrades the car began creeping on its own? Or did it happen after the MBC was changed? Could be a issue with connection, or faulty MBC.

 

[willye_br]

no when the car was stock with only a greddy bov it started doing it i replaves wastegate fuel pump and it seemed to be better but car runs fine it just spikes past 17 when i want it to be 14 max. could a boost leak cause that?

well a fuel pump makes no difference if its stock or upgraded i had the same pump on my 1999 gs non turbo and 450cc injectors (when i was thinking about turboing my gs) and it ran perfect it just send regular amout of gas and if you need more it would be able to send more .

so idk what can be causing this spiking.

 

[SD99GST]

I wont argue back and forth about the pump, but I would recommend reading up on it a little more and you will see that when you get a fuel pump over a 190 you need the afpr. I have heard cases of people running it without it, and say they have had no problems, but i know its recommended and necessary for a safe build.

Kind of wierd that it just happened out of the blue, only thing i could think of is that the actuator went out.. you say you replaced it though, not sure of the one you replaced it with and if it has some kind of adjustment... Does your flapper move freely? I dont think a boost leak would cause this... Also, does the boost climb and stay hi, or just quickly spike then come back down... for now while you diagnose I recommend that you use the stock BCV valve to eliminate the chance of that ebay mbc to be faulty.

 

[willye_br]

Well if you say about the fuel regulator i agree with you since you know been around dsms for longer and tomorrow ill put the stock boost controller and try and ajust the wastegate see what happens =p

 

[Tanro]

have you checked into porting? There are several threads on how to fix boost creep by porting.

 

[hurricanecris24]

Your spiking because of your ebay bc its leaking.

 

[willye_br]

i dont think its the boost controller. i added the boost controller to bring down from 18psi to 14 problem started whle car was stock with a bov

 

[Junfan]

It is most likely the manual boost controller. Remember how those work. They have a spring and a ball against a valve so it takes them a second to respond. It is not uncommon to get a boost spike with a manual boost controller. This is why Hallman makes the MBC with the lightweight ball for a better reaction time.

Porting the turbo housing, exhaust manifold and wastegate hole will help a ton as well.

 

[willye_br]

well its weird because when it didnt have a MBC itr did the same thing i added the cheap MBC to see if it helps im just confused in how can it spike before ???

 

[Junfan]

It spikes because too much exhaust gas is passing through the housing instead of through the waste gate hole but once the wastegate is open all the way the proper amount of air will pass out correctly. It is almost like the wastegate is slow to react and fully open causing you to spike to say 18 and then drop back to 15 or whatever your springs are. You can help this by porting the wastegate flapper hole which I think is like 34mm by default just be careful because you want it to still be sealed when closed otherwise it will always leak which can cause problems getting into boost if the leak is severe.

 

[willye_br]

UPDATE: CAR IS FIXED.

I read up all day and i had a case of one guy having same issues as me with stock wastegate that ran 12psi. someone suggested him top rum a hose DIRECTLY from turbine nipple to wasteghate he said it would create the lowest boost possible at 8psi.

So i thought i have a 17PSI wastegate if i do it directly with that hose i should be runniung lower than that 12-14PSI.
I DID THAT AND BINGO it wont go past 15psi no matter what.when i take off it boosts till 15 and as RPM gets closer to 7ooo it decreases to about 12psi.

IS RUNNING THIS HOSE SAFE THO?

 

[Junfan]

Well, that is basically where you would install a MBC. You go from the nipple on the intake side and then goes into the MBC then out the MBC to the nipple on the wastegate. So it should be fine to leave this I would think.

 

[willye_br]

yea i would think it like this .

instead of running 12,13,14,15 or whatever you set for boost in the MBC your pretty much saying your running at this wastegate boost at all times which is 14PSI in my case so its all good .